Tone-developing unit



March 19, 1929. l. KIMBALL TONE DEVELOPING UNIT Filed July 6j 1925 `\.||I|. lllll Il. lllllllllllllllllllllllllll Il.

was

Patented Mar. 19, 1929.

UNITED STATES PATENT OFFICE.

IRVING- KIMBALL, OF BROOKLNE, MASSACHUSETTS, ASSIGNOR TO GLOBE TECH- NOLIAN CORPORATION, OF BOSTON, MASSACHUSETTS, A CORIPORATION 0F MASSA- cHUsnTrs.

TONE-DEVELOPING UNIT.

Application filed July G,

This invention relates to a tone developing unit, particularly designed for `use in phonographic and radio reproduction of sound. v

rllie object of the invention is, in general, to provide a novel and improved tone developing unit, particularly adapted for use as amplifying and transmitting or conducting apparatus for conveying reproduced sounds and amplifying them Without the production of harshness of tone and the confusion or blurring experienced with. all prior apparatus of this character of which I am aware.

The invention has for a further object to provide sound reproducing apparatus by which the tone, quality, and power of the reproduced sound is improved, so that the sound is reproduced in a perfectly natural tone and with the full power and melody of the original voice or voices, or instrument or instruments, whose sound is being reproduced, andto overcome everything foreign to the reproduction of perfect music, vocal vor instrumental, and in general to vre` produce with original volume, 1nelody and power, every detail of theoriginal sound being produced. Apparatus embodying the present invention is particularly' useful in connection with the reproduction of voice and music by radio receivers, and particu.` larly in loud speaker units thus eliminating, or at least reducing to a minimum, hais-a` ness and indistinctness which have charac` terizcd the apparatus of this character heretofore employed.

1With these objects, and such other objects,

in view as may hereinafter appear, the 1n` vention consists in the tone developing unirI hereinafter described, and particularly de` fined in the claims at the end of this speciiication. f n

in the drawing illustrating the preferred embodiment of the invention, Figure 1 is a vertical sectional view of the improved unit illustrating its use in connection with a radio receiving unitgFig. 2 is a side elevation with. portions in dotted lines illustrating. the em` bodiment of the unit in a phonograph and its manner of use in connection therewith;

Fig.` Sis a front elevation of the unit, viewed` from the mouth thereof; and Fig. 4 is a sectional view on line 1 -4 of Fig. 2.

1925. Serial No. 41,625.

Referring to the dr wing, the present tone developing unit is provided with two sound chambers each of trigonal cross-section, comprising preferably a vertical sound chamber 10, and a horizontal sound chamber 12 combined as a unit, and provision is made at the connection between these chambers to cause sound waves passing from the vertical chamber into the horizontal chamber to be delivered in their natural condition and with fully developed tone, and without causing confusion or blurring of the different come ponents of the waves, an objectionable phenoinenon occurring with all prior types of sound reproducing apparatus of which 1 am aware, and which is readily apparent to the .expert in the indistinctness and the failure from any other source, of the special shape illustrated in Figs. 1 and li. As therein shown, the upper portion of the chamber is rectangular in transverse section, and of a relatively small. dimension, to provide in effect a throat lfinto which the waves are delivered by the diaphragm. The remaining portion of the verticalchamber is preferably formed in the shape of a ilrustum of a pyramid, thus being of trigonal longitudinal cross-section. The lower, and larger, end terminates at one end of the second sound chamber 12, as shown in Fig. 1. The second sound chamber 12 is also rectangular in transverse cross-section, and the upper wall 19 thereof is preferably inclined at an angle, depending upon the volume of amplification desired, producing a trigonal longitudinal openings 23, 2-l, 25, oi Widths progressively increasing from the top to the bottom. oi' the throat 22 of the second sound chamber l2, and in practice I have produced excellent results with this tone portal 2l. of the construction and general shape illustrated in Figs.V 3 and 1l, in which the fertical ivaii 2G ot' the vertical sound chamber l0 extended downwardly across the threat 22 oi the sec-- und sound chamber l2, and the tone portal 2l is cut therein in the term illusti -ted by Figs. 3 and l, providing a series oi projecting portions, impingements or corner pieces 230, 3l, 32, which appear to j, a an important part in the successful operation of t tone developing unit. l have found at i .i the ordinary size ol ampliiier used in connection with the ordinary loud spealtcr unit 'for radio reception, or for an amplilier for the ordinary phonograph, that the port however it is formed, should provide a c itrally arranged series of connected openin *s 23, 24, 25, With the depth of the openings gradually decreasing Yfrom the top to the bottom, and Width of the openings gradually increasing. The eXact proportions may be varied Within limits, but I have found that the relative areas of these openings should be in approximately the proportion illustrated in Figs. 3 and 4. This provides a partition in the throat 22 that impinges on the sides thereof providing a tone portal as high as the throat centrally but as a Whole having a rough trigonal cross-section.

In the operation of the sound amplifying or tone developing unit, either when used in connection with the usual diaphragm ot' a loud .speaker unit 3 4, one of which is conventionally shoivn in Fig. l, or when used in connection with the tone arm l5 and dic..-

phragm of the ordinary phonograph (see F ig. 2), the peculiarly shaped tone portal 2l in combination with the two combined tone chambers l0, 1.2, one arranged to deliver through the portal 2l into the throat ot the second, causes the fundamental sound Waves, I believe, to escape unrestricted through the central opening of the portal, whereas the over-tones are, so to speak, restricted and prevented from intern'iingling With the iundamentals in an objectionable manner by the projecting corner pieces 3 3l, 32, comprising the Walls ot the portal. As to why this peculiarly shaped tone portal 21 should operate in this manner, I can only state that experiment has proven that it will overcome the objectionable indistinctness and harshness apparent to an expert, resulting from the use oi prior constructions o't sound amplifying apparatus, either with radio receiving apparatus, or With phonographs.

The sound chambers may be made of any material tound suitable ior the purpose, but I prefer ei'iiploying tine grained spruce hecause of its particular resonance, and While nvoarro the general shape of these chambers as illustrated in the drawings has been :found to give very satislfactoiy results, I believe that sonic variations co l be used Without disadvantage if the trigonal form is preserved. ln the use of the instrument in f ing sound and particularly music r nu diapliragms, it has been found that the woah over-tones reproduced by the diaphragms may he strengthened by the present apparatus so that the tone is actually developed into a l'ullness and completeness olf tone equal to and in some instances exceedino` that oil' the or' 'nal sound or music being reproduced. while the preiterrcd embodiment olf the invention has been ill ustr ied and described, it. will be understood that the invention may be embodied .in other forms ri'ithin the scope ci" the foil ii,'iiig claims.

Having thus described is claimed is:

l. Tone developing ai'ipara'tus comprising tivo sound chambers, each provided with a relatively narrow throatportion, and with a .vider portion, located so that one chamber is in communication with the throat portion of the other chamber. a tone portal connecting said chambers restricted by side impingements Within the opening between said chambers, and a mouth at the enlarged end of the second chamber through which the amplified sounds emerge.

2. rlone developing apparatus comprising two sound chambers, each provided with a throat portion ci" relatively small sectional dimension, and an end portion of greater sectional dimension, and with the throat portion ot one chamber located innnediately adjacent the enlarged portion ot the ot-her chamber, and a fiat partition of line grained Wood located in the opening at the connection between said throat and enlarged portions ot said chambers, provided with a ccntral tone portal.

8. Tone developing apparatus comprising tivo sound chambers provided 'With throat portions and enlarged end portions, and combined as a unit, and having the throat portion of the second chamber positioned at the enlarged end of the iirst chamber, and means tor connecting said chamber through a tone portal ol rough trigoual section and of les area than the throat of the second chamber.

Il. Tone developing apparatus comprising a vertical sound chamber provided With a throat at the upper end thereot', a horizontal sound chamber provided With a throat communicating `with the loiver portion of the vertical sound chamber, the lower end of one ot the vertical walls oi said vertical sound chamber being extended across the throat of said second sound chamber to the opposite sides thereof and provided with a central tone portal.

5. Tone developing apparatus comprising the invention, what lili) two tone developing chambers each of sectional dimensions progressively increasing from one end thereof toward the other end` and means providing a restricted tone portal between the enlarged end of one chamber and the smaller end of the second chamber for the purpose speciiied, said portal being centrally substantially the height of the opening at the smaller end of the second chamber and decreasing progressively in height from its center toward each side of said opening.

G. Tone developing apparatus comprising a duplex tone chamber each part being of trigonal hingitudinal cross-section arranged at right angles `.to each other with the larger end or the iirst part across the smaller end ot the second part, andhaving an opening from one part to the other that is also of generally trigonal. form and of less area than the area of said smaller end of the second part.

T. In tone developing apparatus, for sound reproducing units, having a duplex tone chamber, an analyzing tone portal intermediate the two parts having substantially fiat side Walls presenting projecting corner l pieces arranged vertically 1n pairs.

8. In tone developing apparatus, for sound reproducing units, having a duplex tone chamber, an analyzing tone portal intermediate the two parts comprising a centrally arranged opening increasing progressively in Width by a series of definite steps.

9. In tone developing apparatus, for sound reproducing unit-s, having a duplex tone chamber, an analyzing tone portal intermediate the two parts comprising a centrally rranged opening of irregular configuration with the depth of the opening gradually decreasing from the top to the bottom and with the Width ot' the opening gradually increasing.

10. lone developing apparatus for sound reproducing units comprising the combined tone chambers l0 and 2() both trigonal in longitudinal cross section having the intermediate tone analyzing portal 21 formed in resonant material, substantially as illustrated and described.

IRVING KIMBALL. 

